1. Field of the Invention
The present invention relates to a hydrocarbon synthesis reaction apparatus, a start-up process thereof, and a hydrocarbon synthesis reaction system.
Priority is claimed on Japanese Patent Application No. 2011-076649 filed on Mar. 30, 2011, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent years, as a process for synthesizing liquid fuels from natural gas, the GTL (Gas To Liquids: liquid fuels synthesis) technique has been developed. This GTL technique includes the steps of reforming a natural gas to produce a synthesis gas containing carbon monoxide gas (CO) and hydrogen gas (H2) as main components, synthesizing hydrocarbons using this synthesis gas as a feedstock gas and using a catalyst via the Fischer-Tropsch synthesis reaction (hereinafter also referred to as the “FT synthesis reaction”), and then hydrogenating and fractionating these hydrocarbons to produce liquid fuel products such as naphtha (raw gasoline), kerosene, gas oil and wax and the like.
In the hydrocarbon synthesis reaction apparatus used in this GTL technique, the hydrocarbons are synthesized by subjecting the carbon monoxide gas and hydrogen gas within the synthesis gas to an FT synthesis reaction inside a reactor main unit that contains a slurry prepared by suspending solid catalyst particles (such as a cobalt catalyst or the like) in a liquid medium (for example, liquid hydrocarbons or the like).
FIG. 7 shows a schematic constitution of a conventional hydrocarbon synthesis reaction apparatus.
This hydrocarbon synthesis reaction apparatus is provided with a synthesis gas supply line 31 in which a synthesis gas containing a carbon monoxide gas and a hydrogen gas as main components is sent by a synthesis gas sending device 3 and the thus sent synthesis gas (SG) is compressed and supplied by a first compressor 34; a reactor 30 which accommodates a catalyst slurry prepared by suspending solid catalyst particles in a liquid to synthesize hydrocarbons by bringing the synthesis gas supplied from the synthesis gas supply line 31 into contact with the catalyst slurry; a gas-liquid separator 38 which separates an unreacted synthesis gas and hydrocarbons discharged from the reactor 30 into a gas and a liquid; an off-gas discharge line 37 which discharges a portion of gas after separation by the gas-liquid separator 38 as an off gas outside a system; a recycle line 32 in which the unreacted synthesis gas after separation by the gas-liquid separator 38 is compressed and recycled into the reactor 30 by a second compressor 35.
A hydrocarbon synthesis reaction apparatus which is provided with the above-described recycle line has been disclosed in Patent Document 1, for example.
Where this type of hydrocarbon synthesis reaction apparatus is used to start-up a system, first, prior to introduction of a synthesis gas, nitrogen, which is an inert gas, is blown in advance into the system for securing gas replacement inside the system and fluidity inside the reactor 30, and the nitrogen is cycled via the recycle line 32. In this case, cycle operation is carried out in a state that the nitrogen to be cycled is secured at a substantial amount. A catalyst slurry inside the reactor is kept in a fluid state by cycling a nitrogen gas and, thereafter, the nitrogen gas is gradually replaced with the synthesis gas. While the synthesis gas amount is kept lower in flow rate (for example, 70%) which is lower than a rated flow rate, the reactor 30 is increased in temperature to raise reactivity (conversion rate). Thereby, the synthesis gas introduced in an amount of up to 100% loads up to shift to operation at a rated flow rate, while confirming stable reaction conditions.